"If they're nekkid, how can you tell they're Amish?"
Educated guess based on:
1. Location, location, location. All of the farms along that particular road for several miles in both directions were Amish owned.
2. Long hair on the girls. Wasn't quite fasionable at the time amongst "English" girls. Shorter hair was.
3. Those ugly bowl-type haircuts most Amish boys have well into their teens.
And yeah, it is rare that you see an Amish or Mennonite girl who could be classified as pretty.
Plain, homely, and moon faced are all adjectives that do normally apply.